Ldp Signaling; Figure 93: Bgp Ad Triggering Ldp Functions - Alcatel-Lucent 7750 SR Manual

LDP Signaling

T-LDP is triggered once the VPN endpoints have been discovered using BGP. The T-LDP
session between the PEs is established when one does not exist. The far-end IP address required
for the T-LDP identification is gleaned from the BGP AD next hop information. The pw-template
and pw-template-bind configuration statements are used to establish the automatic SDP or to map
to the appropriate SDP. The FEC129 content is built using the following values:
•
•
•
Figure 93
completion. It also indicates how some fields can be auto generated when they are not specified in
the configuration.
pw-template 1
vpls 100 customer 1 create
service-mtu 1478
bgp-ad
vpls-id 65535:100
pw-template-bind 1
no shutdown
MPLS-id=1.1.1.134/32
The first command will display the LDP peering relationships that have been established
(Figure
"Both" meaning link and targeted sessions have been successfully established.
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AGI from the locally configured VPLS-ID.
The SAII from the locally configured VSI-ID.
The TAII from the VSI-ID contained in the last 4 bytes of the received BGP NLRI.
below shows the different detailed phases of the LDP signaling path, post BGP AD
Automatic SDP
Far-End:1.1.1.6 (BGP Next-hop)
1
Automatic SDP
Far-End:1.1.1.134 (BGP Next-hop)
FEC 129 Label Exchange
65535:100
Far-End:1.1.1.6 (BGP Next-hop)
PE134
AGI: 65535:100 (VPLS-id)
SAII: 1.1.1.134 (VSI-id)
3
TAII: 1.1.1.6 (VSI-id from BGP AD)
Label: 131063
FEC 129 Label Exchange
Far-End:1.1.1.134 (BGP Next-hop)
AGI: 65535:100 (VPLS-id)
SAII: 1.1.1.6 (VSI-id)
TAII: 1.1.1.134 (VSI-id from BGP AD)
Label: 131067

Figure 93: BGP AD Triggering LDP Functions

94). The type of adjacency is displayed in the "Adj Type" column. In this case the type is
pw-template 1
vpls 100 customer 1 create
service-mtu 1478
bgp-ad
vpls-id 65535:100
pw-template-bind 1
no shutdown
2
65535:100
PE6
MPLS-id=1.1.1.6/32
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7750 SR OS Services Guide
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